The performance of a gravity separator treating coal is commonly determined by plotting a Tromp curve which is basically a plot of partition coefficients against average specific gravity. There are many mathematical models proposed in the literature to represent this curve but selecting the most appropriate model for a given application is not straightforward. As the model is always tentative, it is necessary to examine the adequacy of the model for a particular process. To ascertain the adequacy and the reliability of a model, we consider six different mathematical models available in the literature and determine their suitability for representing the water-only cyclone data. The best model is selected in three steps by adopting a statistical analysis approach. (C) 2009 Elsevier Ltd. All rights reserved.